This invention relates to an error correction arrangement for a digital, electric, length or angle measuring system of the type which includes a measuring division and a scanning unit, in which the measuring division is coupled to a first object and the scanning unit is coupled to a second object moveable relative to the first.
A variety of arrangements for error corrections are known to the art for use in position measuring systems. For example, in German Pat. No. 853 657 there is described an optical measuring system in which a plate is electrically moveable in the beam path in correspondence to the error being corrected.
German Pat. No. 27 24 858 discloses a length measuring system which incorporates a correction system including a link chain, the links of which are adjustable according to the error to be corrected transversely to the measuring direction. A transfer element is provided which scans the link chain and brings about a correcting movement between the scanning unit and the scale of the measuring system. The accuracy of this error correction system is dependent in part upon the length of individual links in the link chain, that is on the number of links per measuring length unit.
German Pat. No. 28 20 753 discloses an arrangement for error correction in a length measuring system in which an error correction profile is integrally formed with a housing which carries a scale. This profile is scanned by transfer element which brings about a correcting movement between a scanning unit and the scale included in the measuring system.
The aforementioned correction arrangements employing transfer elements in the form of swingable angle levers are subject to mechanical wear. Furthermore, such mechanical correction arrangements bring about substantially increased cross-sectional dimensions of the position measuring system in many cases. Such an increase in the size of the position measuring system can be detrimental in many applications, and can restrict the flexibility of use of the measuring system.